In preparing sausage meat for being stuffed into casings it is desirable to deaerate it. The presence of oxygen in the meat increases its rate of deterioration and removal of air produces a denser product, both of which are desirable.
Deaeration has been accomplished in the past by placing sausage meat in a vacuum chamber prior to packing it in casings. In order to deaerate the meat it must be subjected to the vacuum for the time necessary for air to diffuse to the surface of the meat and be carried away. Diffusion is hastened by stirring the meat in the vacuum chamber. In order to provide adequate deaeration, particularly in a continuous process of charging the vacuum chamber with meat and removing deaerated meat to sausage stuffing equipment, vacuum chambers have required a stirrer and a capacity to hold a large quantity of meat.
Diffusion time can be diminshed if meat is introduced into the vacuum chamber as a thin film. It is known to discharge meat into a vacuum chamber through a thin slit in the side of the chamber whereby the meat enters the chamber as a film. Although this method is successful for hastening the deaeration of meat, it has drawbacks.
Some sausage meat is made of very finely subdivided particles having a very homogenous texture, somewhat like mayonaise or peanut butter. Such sausage meat passes easily through a very narrow slit as a stream in the form of a thin film. Other sausage meat has chunks of meat ranging in size up to an inch or more in major dimension. A slit thin enough to make an adequate film of finely subdivided meat will not pass meat having larger particles. A very wide slit capable of handling meat with large particles will not make an adequatly thin film for deaerating meat having very finely subdivided particles.
Even if a slit of the proper width is used, the rate of feed to the vacuum must be controlled so that it approximately equals the rate that meat is withdrawn from the vacuum chamber and passed through a sausage stuffing process. If the flow rate through the slit is too small the shape of the stream will be improper and for a given size slit the maximum flow rate is limited.